The pair told Entertainment Weekly that the first seven episodes of the show's fourth season were "laying the track for... what's going to happen".

"The first seven episodes were an opening act," said Pinkner. "We've seen now what Nina (Blair Brown) is doing to Olivia (Anna Torv) and [the] shape-shifters many times.

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"In this next episode and going beyond, we'll find out who's behind the shape-shifters... and... we'll really start to delve in to the challenges that our characters are going to face in both universes."

Pinkner also confirmed that Peter (Joshua Jackson) will reach out to the scheming Walternate (John Noble) in his efforts to return to his own timeline.

"Peter has some very definite attitudes about Walternate and finds out that in this timeline, things are not entirely as he had suspected them to be," explained the executive producer.

However, co-showrunner Wyman revealed that the sci-fi drama will not immediately return to the original timeline, which was altered when Peter vanished from history.

"For now, we're going to stick to where we are," he said. "But it's going to lead to other things."

Fringe returns to Fox this Friday at 9/8c. The show airs on Sky1 in the UK.